Boutonniere deformity is defined by which mechanism?

Study for the NBCOT Hand Injuries and Intervention Test. Prepare with flashcards and multiple choice questions, each question offers hints and explanations. Get ready for success!

Multiple Choice

Boutonniere deformity is defined by which mechanism?

Boutonniere deformity happens when the central slip of the extensor mechanism at the PIP joint is disrupted. The central slip normally extends the PIP, so when it is torn, the PIP loses its extension force. The lateral bands then shift toward the palm and act as flexors of the PIP, pulling the PIP into flexion. Meanwhile, those same lateral bands continue to pull on the distal phalanx in a way that extends the DIP, or leaves it extended, so the DIP ends up hyperextended. The result is a finger that sits with the PIP flexed and the DIP hyperextended. This pattern distinguishes it from injuries like mallet finger (DIP alone flexed) or MCP dislocations, which involve different parts of the extensor mechanism or joints.

Boutonniere deformity happens when the central slip of the extensor mechanism at the PIP joint is disrupted. The central slip normally extends the PIP, so when it is torn, the PIP loses its extension force. The lateral bands then shift toward the palm and act as flexors of the PIP, pulling the PIP into flexion. Meanwhile, those same lateral bands continue to pull on the distal phalanx in a way that extends the DIP, or leaves it extended, so the DIP ends up hyperextended. The result is a finger that sits with the PIP flexed and the DIP hyperextended. This pattern distinguishes it from injuries like mallet finger (DIP alone flexed) or MCP dislocations, which involve different parts of the extensor mechanism or joints.

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